A radiation dosimeter of this type comprises essentially a pump for inducing a flow of ambient air through a filter, a radiation detector positioned so as to receive alpha emissions from decay products entrapped by the filter, and electronic circuitry for processing and counting pulses generated in response to the detection of alpha emissions. The pulse count is stored and subsequently read into a central readout unit at the end of a working day. The product unit, which is typically a general purpose computer capable of addressing the dosimeter circuitry by an appropriate code, maintains a record of the miner's "working level hours" corresponding to the accumulative exposure to radiation as measured by the dosimeter.
One such radiation dosimeter is described in U.S. Pat. No. 4,055,762 to John Durkin, issued Oct. 25, 1977 and entitled "Radon Daughter Dosimeter".
Although the principle of this method of measuring accumulative exposure to alpha radiation is well known, there have until now been serious difficulties in its practical application to field use. One difficulty has been to assemble the essential components of the equipment in a convenient package which can be worn by a miner without encumbering him in his work. Another difficulty has been to construct a unit which would have the required sensitivity and be sufficiently robust to withstand rough handling during use.